Method and system for international roaming and call bridging

ABSTRACT

Disclosed is an enhanced system and method for bridging calls across telecommunications networks, including an illustrative application of the invention as it relates to international roaming among prepaid wireless subscribers. For instance, whenever wireless subscribers roam internationally they may invoke the system by keying in an Unstructured Supplementary Service Data (USSD) short code followed by the number to be dialed. Said subscriber&#39;s prepaid account is then decremented in real-time (until such account is fully depleted). A key feature of the disclosure generally is the bridging of the call legs between the wireless subscriber initiating the telephone communication and that of the receiving party through a series of general purpose databases and computers without requiring modifications to existing core network or handset infrastructure.

BACKGROUND ART

[0001] International roaming and more generically, the bridging of callsacross telecommunications networks is well detailed in the prior artliterature related and industry know-how. For instance, U.S. PatentApplication Pub. No. 2002/0061745 by Ahn et al., entitled RoamingService System for GSM Service Subscriber in CDMA Service Area, andMethod for Registering Locations and Transmitting and Receiving Signalsand Short Messages using the System, calls for the installation of aGSM-type SIM card into the CDMA terminal; our invention of presenthowever remains independent of any such subscriber modification and/orregistration.

[0002] Similarly, U.S. Pat. No. 6,075,855 to Christiansen et al.,entitled Method of Accessing a SCP in an ISUP Network with PartialRelease details art relevant to call set-up and clearing forintermediate access to a SCP in an ISUP network. Nevertheless, the artdisclosed therein remains tied to the loop-back (‘hairpin’) trunktechnique; a highly undesirable technique given today'stelecommunications infrastructure, as it redundantly ties up trunks andrelated network resources. Indeed the art of the present inventionremains independent of any such looping and goes beyond much of theobviousness of that disclosed art. Other related technology, as U.S.Pat. No. 6,393,289 to Bunting et al., entitled Apparatus, Method andSystem for Wireless Telecommunication Session Control by an AdjunctNetwork Entity, revolves around the interpretation of an ANSI-41 commandby an network adjunct. Under that disclosure, the network adjunct willin turn allow the call to proceed, hair-pin the call, or invoke otherANSI-41 directives in order to instruct the switch to route the callwithout hair-pining the call through the network adjunct. REFERENCESCITED: U.S. Patent Application 20020061745 May 2002 Ahn et al. 455/432U.S. Pat. No. 6,393,289 May 2002 Bunting et al. 455/445 U.S. Pat. No.6,075,855 June 2000 Christiansen et al. 379/209.01

Other References

[0003] GSM 03.90, Digital cellular telecommunications system (Phase 2+);Unstructured Supplementary Service Data (USSD)-Stage 2

[0004] GSM 09.02, Mobile Application Part (MAP) specification

[0005]3GPP2 N.S0023, Network Support for MDN-Based Message Centers

[0006] TIA TR 45.2,IS-841, TIA/EIA-41-D Based Network Enhancements forMDN Based Message Centers

[0007] TIA/EIA ANSI-41 Cellular Radiotelecommunications IntersystemOperations

TECHNICAL FIELD

[0008] The present invention relates generally to wirelesscommunications and services; and more specifically, to an improvedmethod and system for the bridging of calls across telecommunicationsnetworks.

SUMMARY OF THE INVENTION

[0009] Particular attributes of traditional Intelligent Network (IN)environments have inherently constrained the development and geographicscope of applications which utilize the capabilities of today'snetworks. The asynchronous development cycles of traditional INinfrastructure vendors have led to variants in vendors’ implementationsof IN technologies. This point, as well as the inclusion of proprietaryextensions to IN signalling protocols, have made interworking of INservices an ongoing issue faced by wireless carriers—particularly whereinterworking between a mix of vendor platforms is required. Theselimitations have effectively precluded the geographic scope of popularwireless ‘prepaid’ services to areas within the operating region of agiven carrier where the carrier has deployed core network infrastructure(e.g. Home Location Registers (HLRs), Mobile Switching Centers (MSCs),Service Control Points (SCPs)) associated with a common vendor.

[0010] As such, the improved method and system for Call Bridging andInternational Roaming disclosed herein is an innovative networkapplication, enabling prepaid subscribers to place calls wheneverroaming outwith their home network or in the invocation of otherapplications which involve bridging the subscriber to another subscriberor to a service provider.

[0011] Upon being initiated, the system sets up calls to both theoriginating and destination party, and bridges them together. The callbridge is in effect ‘forced’.

[0012] Specifically, the calls are bridged using the switching fabric ofa given Mobile Switching Center using the procedures and operationsassociated with the SS7 ISDN User Part (ISUP) protocols in an innovativemanner as disclosed herein. An illustrative aspect of the disclosed artalso permits mobile phone operators to log and transact calls made byprepaid subscribers when they are away from their homenetwork-effectively expanding the geographic scope of prepaid wirelessservices.

[0013] Although the method and system disclosed, by and large employs aseries of general purpose databases, filters and computers to achieveits ends, the bona fide distinctiveness of the invention resides in theso-called call setup module (CSM), which principally incorporates muchof the functional and operative aspects of the invention.

[0014] A subscriber may invoke the call-bridging procedures byinitiating a message to the CSM. A variety of mechanisms may be utilizedby a given subscriber for the purpose of sending a message. Thesemessaging mechanisms may include, but are by no means bounded by, ShortMessage Service (SMS), Unstructured Supplementary Service Data (USSD),Internet browser, or a voice-based call using Dual-Tone-Multi-Frequency(DTMF) Interactive Voices Response based technologies. The message maybe routed directly via existing telephony protocols or may be routedindirectly via a messaging gateway. The information provided via themessaging mechanism will typically include the identity of theoriginating subscriber, the destination address, and the service to beactivated.

[0015] The messaging gateway will also typically initiate the CallBridging procedure via an Application Programming Interface (API) whichwill include a number of parameters including but not limited to theoriginating subscriber address, terminating subscriber address, and atransaction identifier. The purpose of the transaction identifier beingto uniquely correlate a given request with other messages which may bereceived asynchronously including, but not limited to, a confirmationresponse. Practitioners skilled in the art shall recognize that avariety of object oriented application programming interfaces (e.g.Common Object Request Broker Architecture (CORBA), Extensible MarkupLanguage (XML)) will serve the purpose of notification without affectingthe intent and scope of the present invention.

[0016] The CSM may also autonomously initiate the call-bridgingprocedure via a request initiated by programmatic instructions stored inan software application resident in the CSM. For example, the CSM mayinvoke the call-bridging procedure at a given prescribed time in orderto bridge a subscriber to a recording for a wake-up service stored inthe CSM.

[0017] The CSM performs a syntax and validity check to determine if therequest as received is well formed. It may also retrieve thesubscriber's location in the Home Location Register (HLR) to assist thebilling system in correctly rating the call. Additionally, the CSM isalso responsible for normalizing the called number and for eventlogging.

[0018] Indeed, the CSM requests the initiation of two call attemptsfirst to the subscriber (originating Mobile Station Integrated ServicesDigital Network Number (MSISDN)) and, on successful establishment,subsequently to the requested ‘destination’. The call legs are eachrouted to a defined circuit of the ISUP loop around configured in thenetwork by defining the CIC for the call legs as equivalent.

[0019] The Bridging method, and its non-limited illustrative applicationto International Roaming, specifically utilizes a Loop Around mechanismin order to leverage the inherent resilient switching fabric of theNetwork Operator's MSC. In a standard configuration a loop aroundfacility is configured with an adequate number of circuits in order toaccommodate the anticipated traffic requirements associated with themethod. The MSC is configured to treat each end of the call as atrunk-group to a virtual MSC associated with a given SS7 point code(that is, from the perspective of the MSC, the loop-around facility istreated as two trunk-groups which terminate at another MSC).

[0020] The method will initially establish a call towards theoriginating mobile pre-paid subscriber utilizing the attributes (CircuitIdentification Code) associated with one end of the loop-aroundfacility. Note that from the perspective of the loop-around equippedMSC, the loop-around equipped MSC will appear to be receiving an ISUPcall from another MSC. The loop-around equipped MSC will utilize itsexisting translation tables in order to direct the call via theappropriate out-bound facility in order to establish an ISUP call to theoriginating pre-paid mobile subscriber. Note that all ISUP traffic (e.g.the ACM, ANM, REL, RLC messages) associated with end of the loop-aroundfacility which is used to establish a call to the originating subscriberwill be terminated by the CSM. When the originating mobile subscriberhas answered the phone, an ANM message will be received by the CSM. TheCSM will in turn initiate the second leg of the call to the destinationsubscriber located in the PSTN (Public Switched Telephone Network) viathe other end of the loop-around facility. The CSM will necessarilycorrelate the Circuit Identification Codes so that the same facility(time-slot) is utilized at each end of the loop-around trunk-group for agiven call. The loop-around equipped MSC will similarly utilize itsexisting translation tables in order to direct the call via theappropriate out-bound facility to the destination subscriber via thePSTN. When the terminating PSTN subscriber has answered the phone, anANM message will be received by the CSM. At this point in time, theloop-around equipped MSC will effectively bridge the calls together viathe switching fabric of the loop-around equipped MSC and the correlatedtime-slot/facility of the loop-around trunk-group.

[0021] Should the destination number be otherwise busy, an audible busysignal from the receiver will be connected to the call originator. Thisconnection will be kept shortly, and then released. A message shall thenbe delivered to the call originator in this case, indicating thedestination number is busy. The message may be delivered via severalmechanisms, including but not limited to, SMS, USSD, and Simple MailTransfer Protocol (SMTP) based technologies.

[0022] Once the CSM detects a disconnection from either party byreceiving an ISUP REL message, the CSM will complete the releasesequence on that leg of the call as well as initiate a release sequenceon the correlated facility on the other side of the loop-aroundtrunk-group in order to release the circuit-switched facilities towardsthe other party. Note that if the release signal is initiated from theterminating PSTN subscriber, the CSM may optionally initiate an ISUPcall origination sequence via the loop-around facility in order todirect the originating pre-paid subscriber to an IVR application for thepurpose of receiving further instructions from the originatingsubscriber.

[0023] Indeed, these features and other such advantages of the presentinvention shall readily become apparent from the following descriptionand accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 illustrates a configuration of the call bridging method andsystem in a sample telecommunications system in accordance with anon-limiting embodiment of the present invention;

[0025]FIG. 2 illustrates a typical, non-limiting embodiment of thesystem level architecture employed in an exemplar articulation of thepresent invention involving call establishment procedures for prepaidmobile phones;

[0026]FIG. 3 details a non-limiting call-flow of a successful callset-up, illustrative of the bridging of the call legs in but onearticulation of the present invention involving call establishmentprocedures for prepaid mobile phones.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] With reference now to FIG. 1, which presents a configuration ofthe invention in an exemplar telecommunications system. Members skilledin the art will appreciate that the illustrated network elements do notrepresent all of the physical nodes used to realize a public mobiletelecommunications network. Indeed, those members shall also recognizethat additional transport and signalling facilities may be utilized inorder to establish connectivity among the network elements as generallydescribed in standards and specifications including, but not limited to,ANSI-41 and GSM 9.02. Detailed depictions of well known architecturesand network configurations are omitted so as not to obscure the art ofthe present invention with superfluous detail.

[0028] Again referring to FIG. 1, the SS7 12 network provides signallingconnectivity among a number of network elements in the public networkincluding Service Centers 13. Signalling connectivity via signallinginterfaces and transport mechanisms 11 can also be provided by otherprotocols including the Stream Control Transmission Protocol (STCP) andSession Initiation Protocol (SIP) specified by the Internet EngineeringTask Force (IETF). The Switching Center 13 provides for a source andsink of communications traffic as the Switching Center 13 servessubscribers (not shown) via land-line and mobile stations (not shown).The Switching Center 13 serves mobile stations (not shown) via basestations (not shown) and radio links (not shown). The connectivitybetween the mobile station and a given destination point such as anothermobile station (not shown) or another fixed station (not shown) isprovided via the Switching Center 13 which in turn provides SS7connectivity and transport connectivity via the Public or PrivateNetwork 15 via bearer transport mechanisms (e.g. E1 or T1 basedtransport facilities) 14 24. The Switching Center 13 also serves totandem traffic received from Public or Private Network 15 to anotherdestination point (not shown) in the Public or Private Network 15 aswell as alternative Switching Centers (not shown) or adjunct devices(not shown) which are directly interconnected with the Switching Center13. The Call Bridging Server 10 has direct or indirect connectivity tothe network elements of the telecommunications network including, butnot limited to, the Switching Center 13 using industry standardprotocols such as SS7 or SCTP.

[0029] Still in consideration of FIG. 1, the Switching Center 13 isequipped with a loop-around transport facility 16. The loop-aroundtransport facility is a transport facility which provides connectivitybetween two ports 17 18 on the Switching Center 13. A given circuit ortime-slot in the loop-around transport facility 16 is terminated to theports 17 18 on the Switching Center 13. The circuit in the loop-aroundtransport facility 16 is correlated to two unique SS7 ISDN User PartCircuit Identification Codes for the given Switching Center 13. Eachport 17 18 which is associated with a given end-point of the loop-aroundfacility is associated with a unique Circuit Identification Code. Thoseskilled in the art will recognize that several analogue or digitaltransmission systems may be used for the purpose of establishing theloop-around facility including those based on E1 and T1 transmissionstandards. Details pertaining to the electro-mechanical nature as wellas encoding mechanisms associated with well known transmissionmechanisms are omitted so as not to obscure the description of thepresent invention with unnecessary detail.

[0030] Still in consideration of FIG. 1, the Call Bridging Server 10will initiate the call bridging procedure by initiating a call-set upprocedure to a destination point served by the Switching Center 13 or bythe Public or Private Network 15 via the switching fabric 21 andapplicable interface port 19 of the Switching Center 13. The destinationpoint may be a land-line or mobile station as well as a adjunct nodewhich provides a telecommunications service (for example an interactivevoice response based service). The Call Bridging Server will be equippedwith a unique SS7 identifier (signalling point code) and will appear tobe an adjacent adjunct to the Switching Center 10. Details associatedwith well known call establishment signalling mechanisms, operations,and procedures are omitted so as not to obscure the description of thepresent invention with unnecessary detail. The call-set up procedurewill utilize an Initial Address Message (IAM) which will include aCircuit Identification Code (CIC) associated with one end of the looparound transport facility which in turn is associated with one port 17on the Switching Center 13. The end of the loop around-facilityassociated with the initial call initiated by the Call Bridging serverwill be identified by a unique CIC for that Switching Center 13. Fromthe perspective of the loop-around equipped Switching Center 13, theSwitching Center 13 will appear to be receiving an IAM messageassociated with an incoming call from the Call Bridging Server 10. Theloop-around equipped Switching Center 13 will utilize its existingtranslation tables in order to direct the call via its internalswitching fabric 21 to the appropriate transport facility which mayinclude an outbound transport facility 14 to a destination point in thePublic or Private Network 15 or a termination point directly served bythe Switching Center 13 (for example, a mobile station served by a basestation). Subsequent call-establishment procedures involving the receiptand processing of SS7 call establishment messages associated with thecall initiated by the Call Bridging Server 10, including but not limitedto, the Address Complete Message (ACM) and the Answer Message (ANM) willbe directed to the Call Bridging Server 10 via the Switching Center 13and the SS7 Network 12. Each SS7 call establishment message associatedwith the call initiated by the Call Bridging Server 10 directed to theCall Bridging Server 10 will include the CIC associated with the circuitor time-slot of the loop around transport facility 16 which isterminated on the Switching Center 13 via a port 17. Subsequent to thedestination point answering the call initiated by the Call BridgingServer 10, an ANM message will be received by the Call Bridging Server10 message via the Switching Center 13 and SS7 Network 12. The CallBridging Server will in turn initiate the second leg of the call to asecond destination point served by the Switching Center 13 or by thePublic or Private Network 15 via the switching fabric 22 and applicableinterface port 20 of the Switching Center 13. The second destinationpoint may be a land-line or mobile station as well as a adjunct nodewhich provides a telecommunications service (for example an interactivevoice response based service). The call-set up procedure will utilize anIAM which will include a second Circuit Identification Code (CIC)associated with the other end of the loop around transport facilitywhich in turn is associated with a second port 18 on the SwitchingCenter 13. The Call Bridging Server 10 will correlate the CircuitIdentification Codes associated with the loop-around facility so thatthe same circuit (time-slot) is utilized at each end of the loop-aroundtrunk-group for a given call. From the perspective of the loop-aroundequipped Switching Center 13, the Switching Center 13 will appear to bereceiving an IAM message associated with a second incoming call from theCall Bridging Server 10. The loop-around equipped Switching Center 13will utilize its existing translation tables in order to direct thesecond call via its internal switching fabric 22 the appropriatetransport facility which may include an outbound transport facility 24to a destination point in the Public or Private Network 15 or atermination point directly served by the Switching Center 13 (forexample, a mobile station served by a base station). Subsequentcall-establishment procedures involving the receipt and processing ofSS7 call establishment messages associated with the call initiated bythe Call Bridging Server 10, including but not limited to, the ACM andthe ANM will be directed to the Call Bridging Server 10 via theSwitching Center 13 and the SS7 Network 12. Each SS7 call establishmentmessage associated with the second call initiated by the Call BridgingServer (10) will include the second CIC associated with the circuit ortime-slot of the loop around transport facility1 6 which is terminatedon the Switching Center 13 via a port 18. Subsequent to successfulinitial contact with the second destination point, an ACM message willbe received by the Call Bridging Server 10 via the Switching Center 13and SS7 Network 12. The initial destination point may be able to hearcall progress tones (for example, ringing tone) at that point in time byvirtue of the connectivity established in the Switching Center 13 viathe connectivity established between two ports 19 20 via the switchingfabric 21 22 and the loop around transport facility 17 connected to theSwitching Center 13 via the facility termination ports 17 18. Subsequentto the second destination point answering the second call initiated bythe Call Bridging Server 10, an ANM message will be received by the CallBridging Server 10 message via the Switching Center 13 and SS7 Network12. The leg of the call to the first destination party will be bridgedto the leg of the call to the second destination party via the switchingfabric 21 22 of the Switching Center and the loop-around transportfacility 16. That is, the loop around transport facility 16 will bridgethe two destination parties utilizing the switching fabric 21 22 of theSwitching Center 13. The two parties may commence communications via theestablished bearer path which includes the two legs of the callinitiated by the Call Bridging Server 10 and the loop-around transportfacility. Subsequent to the release of a leg of the call via one of thedestination parties, a Release Message (REL) will be will be received bythe Call Bridging Server 10 message via the Switching Center 13 and SS7Network 12 for the leg of the call associated with the initiated callrelease. The received REL message will contain the CIC associated withthe leg and destination party which initiated call release. The CallBridging Server will initiate call-release procedures for the other legof the call by sending a REL message with a CIC associated with the portand leg of the call of the other destination party. Subsequent to thesuccessful release of the call, a Release Complete (RLC) message will bereceived by Call Bridging Server 10 message via the Switching Center 13and SS7 Network 12. The Call Bridging Server 10 will continuecall-release procedures by sending a RLC message with a CIC associatedwith the port and leg of the call of the destination party whichinitiated the call-release procedure. Those skilled in the art willrecognize that other SS7 messages may be initiated, propagated, andregenerated via the Switching Center 13 and Call Bridging Server withoutdiluting the material aspects of the invention. Those skilled in the artwill also recognize that the Call Bridging Server 10 may initiate thecall termination procedure on either leg of the call based onprogrammatic instructions for a particular telecommunications service.For example, if it is determined that the account for a giventelecommunications service has been depleted the Call Bridging Server 10may terminate the service by initiating call release procedures for bothlegs of the call. Those skilled in the art will also recognize that theCall Bridging Server 10 may elect not to propagate call releaseprocedures associated with one leg of a call and may initiate a callupon completing the call release procedures for a single leg of thecall. For example, upon completing the call release procedures for oneleg of the call, the Call Bridging Server 10 may initiate a call to asubsequent destination such as an Interactive Voice Response system forthe purpose of relaying information or receiving further instructionsfrom the subscriber connected to the loop around facility via theswitching fabric of the Switching Center and outbound transportfacility.

[0031] With reference to FIG. 2, whenever a prepaid wireless subscriberis roaming outwith his/her home network they may invoke the system bykeying in an Unstructured Supplementary Service Data (USSD) short code,*121* for instance, followed by the number to be dialed 201. The USSDmessage is automatically routed to the USSD Gateway 203 on the homenetwork via the Visitor Location Register (VLR) / Home Location Register(HLR) 202. The USSD message is routed to the USSD gateway using themethods, operations, and protocols specified in GSM 03.90 and GSM 09.02as amended from time to time. Details associated with well known messagedelivery methods and procedures are omitted so as not to obscure thedescription of the present invention with unnecessary detail. Thoseskilled in the art will recognize that a variety of alternativemechanisms may be utilized by a given subscriber for the purpose ofinvoking a service by sending a message. These mechanisms include, butare by no means bounded by, Short Message Service (SMS, Internetbrowser, or a voice-based calls using Dual-Tone-Multi-Frequency (DTMF)Interactive Voices Response based technologies.

[0032] Again with reference to FIG. 2, the call request is forwarded tothe general purpose Call Bridging Server (which houses the Call SetupModule and the International Roaming Application—a specific instance ofthe Bridging application for illustrative purposes) 204. The request maybe received via an Application Programming Interface (API) which willinclude a number of parameters including but not limited to theoriginating subscriber address, terminating subscriber address, and atransaction identifier. The purpose of the transaction identifier beingto uniquely correlate a given request with other messages which may bereceived asynchronously including, but not limited to, a confirmationresponse. Practitioners skilled in the art shall recognize that avariety of object oriented application programming interfaces (e.g.Common Object Request Broker Architecture (CORBA), Extensible MarkupLanguage (XML)) will serve the purpose of notification without affectingthe intent and scope of the present invention. Those skilled in the artshall also recognize that the request may be received by the CallBridging Server via telephony protocols as specified in GSM 03.90 andGSM 09.02 as amended from time to time. Details associated with wellknown message delivery methods and procedures are omitted so as not toobscure the description of the present invention with unnecessarydetail.

[0033] Still in consideration of FIG. 2, where the account balance(query 205) is greater than a predesignated threshold the InternationalRoaming Application (IRA) may initiate a Send Routing Information (SRI)message to the HLR with a view to obtaining the Mobile SubscriberRoaming Number (MSRN) and VLR for the said roaming subscriber 206.Keeping with this illustration, the (international roaming) bridgingapplication also screens service access; dictating for example, thatonly certain numbers may be dialed, thereby preventing the very real andwidespread concern among wireless providers for abuse of service andother instances of fraud.

[0034] Employing the subscriber/originator's MSISDN (or in alternateembodiments, the MSRN), the IRA formulates an ISUP Initial AddressMessage (IAM) message which is directed to the Mobile Switching Center(MSC) 207 via the SS7 network (not shown). The ISUP IAM message willcontain a Called Party Number parameter which is set to the MSISDN (orin alternate embodiments, the MSRN) and will contain the CIC associatedwith one end of the loop-around arrangement.

[0035] Still in consideration of FIG. 2, The MSC then proceeds toestablish the call to said roaming subscriber in Visited MobileSwitching Center (VMSC) 208 via the Public Switched Telephone Network(PSTN) (not shown).

[0036] The successful set-up of the first call leg triggers theInternational Roaming Application to initiate set-up of second call leg(not shown). Initiating the second call over the corresponding circuitof the loop around circuit bridges the two calls together and the calledparty on the first leg can hear the call progress (alerting) tones onthe line). Said act thereof will further trigger to the Service ControlPoint (SCP) to verify sufficient balance 209, and initiates rating ofthe calls. In alternate embodiments, prefix digits are prepended to thedestination number to aid the SCP in rating the call appropriately. Inother alternate embodiments, the IRA may directly adjust the accountbalance of the SCP via an interface and protocol supported by the SCP.Correspondingly, when either the first of second leg hangs up, the otherleg of the call is also disconnected by the International RoamingApplication (the MSC would trigger the SCP to stop rating the call, anddeduct from the subscriber's account accordingly).

[0037] Now in reference to FIG. 3, at 101 the subscriber initiates aUSSD request which is relayed to the USSD Gateway via the SS7 network.The USSD Gateway transfers the request to the International RoamingApplication (IRA); contained within which is the Call Control Module(CSM), which determines if said subscriber is within the designatedserving region, and in alternate embodiments, the status and nature ofthe subscriber's balance 102.

[0038] Now still in consideration of FIG. 3, The IRA will initiallyestablish a call towards the originating mobile pre-paid subscriberutilizing the attributes (i.e. Circuit Identification Code) associatedwith one end of the loop-around facility. Note that from the perspectiveof the loop-around equipped MSC, the loop-around equipped MSC willappear to be receiving an ISUP call from another MSC. The loop-aroundequipped MSC will utilize its existing translation tables in order todirect the call via the appropriate out-bound facility in order toestablish an ISUP call to the originating pre-paid mobile subscriber viathe PSTN. Note that all ISUP traffic (e.g. the ACM, ANM, REL, RLCmessages) associated with the loop-around facility which is used toestablish a call to the originating subscriber will be terminated by theCSM. The end of the loop around-facility associated the call establishedto the originating pre-paid subscriber will be identified by a uniqueCIC for that MSC. When the originating mobile subscriber has answeredthe phone, an ANM message will be received by the CSM. The CSM will inturn initiate the second leg of the call to the destination subscriberlocated in the Public Switched Telephone Network (PSTN) via the otherend of the loop-around facility. The end of the loop around-facilityassociated the call established to the destination subscriber will beidentified by a second unique CIC for that MSC.

[0039] The CSM will necessarily correlate the Circuit IdentificationCodes associated with the loop-around facility so that the same facility(time-slot) is utilized at each end of the loop-around trunk-group for agiven call. The loop-around equipped MSC will similarly utilize itsexisting translation tables in order to direct the call via theappropriate out-bound facility to the destination subscriber via thePSTN. When the terminating PSTN subscriber has answered the phone, anANM message will be received by the CSM. At this point in time, theloop-around equipped MSC will effectively bridge the calls together viathe switching fabric of the loop-around equipped MSC and the correlatedtime-slot/facility of the loop-around transport facility 103.

[0040] The originating party will be able to hear the usual callprogress tones upon receipt of the second ACM at the loop-aroundequipped MSC. The account associated with the originating subscriber(where prepaid) is decremented using standard CAMEL/INAP messagingsequences on the so-called ‘PSTN’side of the call. In alternateembodiments, the destination number may optionally be prefixed to invokea special charge in the SCP. In other alternate embodiments, the CSM maydirectly adjust the subscriber balance via a protocol and interfacesupported by the SCP.

[0041] At 104, the call is connected.

[0042] While the foregoing describes what are considered to be thepreferred embodiments of the invention, it is understood that variousmodifications may be made therein and that the invention may beimplemented in various forms and alternate embodiments, and indeed thatit may be applied in numerous applications, only some of which have beendescribed. The claims are intended to cover all such modifications andvariations which fall within the true scope of the invention.

What is claimed is:
 1. A comprehensive method, fully integrated withexisting wireless technologies and infrastructures, for bridging callsacross telecommunications networks.
 2. The method of claim 1, whichdeals principally with existing limitations and problems associated withinternational roaming.
 3. The method of claim 2, wherein saidinternational roaming issues remain particular to prepaid wirelesssubscribers.
 4. The method according to claim 2, wherein internationalroaming refers to that inclusive situation where a particular wirelesssubscriber uses his/her wireless or mobile device outwith a specifiedtariffed geographic area as defined by the service provider (usuallytermed the “home” area).
 5. The method of claim 1, concerning andinvolving a computer program product (the ‘call setup module’ (CSM)) forimplementing the international roaming application, comprising: a.computer readable memory medium; and b. computer program includinginstructions for: i. receiving and handling requests to initiate callsvia a plurality of interfaces (as with a Common Object Request BrokerArchitecture (CORBA) interface for instance) from a further plurality ofMessaging gateways (of which Unstructured Supplementary Service Data(USSD) represents an instance); and ii. performing the requisite syntaxand validity check to determine if said request is well formed; and iii.determining said subscriber's location in the Home Location Register(HLR); and iv. normalizing the called number and for event logging. 6.The method of bridging calls across telecommunications networks, saidmethod comprising: a. a server requesting the initiation of two callattempts to two destinations; and b. a Switching Center equipped with aloop around transport facility which is terminated on suitably equippedports or interfaces on the Switching Center.
 7. The method of claim 6,wherein the destinations are identified via applicable network addressidentifiers.
 8. The method of claim 7, where network address identifiersinclude Mobile Station Integrated Services Digital Network (MSISDN) andother E.164 addresses.
 9. The method of claim 6, whereby the call legsare each routed to a defined circuit of the ISUP loop around transportfacility.
 10. The method of claim 9 whereby a circuit or time-slot inISUP loop around transport facility is associated with two CircuitIdentification Codes.
 11. The method of claim 9 whereby two calls arebridged using the switching fabric of a Switching Center by initiatingcalls which are associated with the Circuit Identification Codesassociated with the ISUP loop around transport facility.
 12. The methodof claim 6 whereby the server will receive the messages associated witha call release sequence for one of the established calls.
 13. The methodof claim 12 whereby the server will complete the call release proceduresfor the leg of the call for which a call release indication wasreceived.
 14. The method of claim 13 whereby the server will initiateand complete the call release procedures for the for the other leg ofthe call.
 15. The method of claim 12 whereby the server will initiatethe call bridging procedure to another destination using the CircuitIdentification Code associated with the released call leg.
 16. Themethod of claim 6 whereby the server will initiate and complete the callrelease procedures for a given leg of the call.